Comes through or, alternatively, is routed (5,3)
I believe the answer is:
rides out
'comes through' is the definition.
The answer and definition can be both to do with fundamental existence as well as being verbs in their -s form.
Maybe you can see a link between them that I don't see?
'alternatively is routed' is the wordplay.
'alternatively' indicates anagramming the letters (I've seen this in other clues).
'is'+'routed'='isrouted'
'isrouted' with letters rearranged gives 'RIDES OUT'.
'or' is the link.
Can you help me to learn more?
(Another definition for rides out that I've seen is " Survives intact".)